Injection molding machine



y 1,. 1950 c. E. MAYNARD 2,514,884

' INJECTION MOLDING MACHINE Filed May 25, 1948 4 Sheets-Sheet 1 I N v a N+ u R1 amass 5. MA )WHRD a'hpmvmzz A ys- July'll, 1950 c. E. MAYNARD 2,514,884

INJECTION MOLDING MACHINE Filed May 25, 1948 I 4 Sheets-SheetZ INVEN+URZ July 11, 1950 C. E. MAYNARD INJECTION MOLDING MACHINE Filed May 25, 1948 4 Sheets-Sheet 5 :1; N VEN 4-51 amass 5 MA Y/Y/i/PD pi, alm? y 1950 c. E. MAYNARD v 2,514,884

INJECTION MOLDING MACHINE Filed May 25, 1948 4 Sheets-Sheet 4 OIL SUPPLY MIXING INVENLDR: C/MRLES E. MA YNHRD b A-H- s Patented J l 11, 1950 1 N E O G MACH N Charles Edgar Maynard, Northampton, Mass as- Signor to Pro-Phy-Lac-Tic Brush Company, Northampton, Mass, el-corporation of Delaware Application May 25, 1948, Serial No. 29,154 f 4Claims.

In a previous application, Serial No. 591,910, filed May 4,1945, new 'U. S. Patent No. 2,442,368 I described an improved process of making moldforcedthrough an orifice'into aclosed mold. This process is employed with such synthetic molding materials aLscellulose acetate, methacrylate acid esters, styrene, .vinyl and 'vinylidene chlorides,

ethyl'cellulose, phenol formaldehyde, urea form aldehyderesins, etc. Ordinarily these materials are used in granular or powder form. "In the process of myfinvention these materials were fpre-plasticiz ed by the heat developed by internal friction due to working the material priorto molding." The present invention relatesto a machine for carrying out, the. process described in 'said application and other procedure hereinafter described The machine of the present invention will best be understood from the following. description in conjunction with theaccompanying drawings, in

which:

,Fig.-1 is a t Fig. 21s a section taken on the line 2 -2 of Fig. 3 shows certain parts of Fig. 2 in a dif ferent position; I I it "Fig. 4 is a sectiontaken on the line 4-4 of M g; 5 is a view similar to Fig 4 showing adifferent position of some ofthe parts; I T Fig. 6 is a detailviewofasubstitute part; and Fig. 7 is a diagrammatic yiew. In-thedrawings, the machine of the invention is provided with a ram I reciprocally movable in an injection cylinderZ and operated by a piston 3 mounted in a cylinder ,4 which derives fluid pressure from hydraulic lines indicated at 5-5. The forward end of-the cylinder 2 isequipped with a, nozzle 6 which extends through platen 7 which is one of a pair of platens l and ,8. A port 9 is formed in the cylinder 2 intermediate the nozzle 6 and the face of the ram when it is fully retracted to theposition shown in Fig. 1. This ports is closed by cylinder segments NJ and H (see Fig. 2) and, when open, connects the cylinder 2 with a closed. conduit 12 which communi cates with a chamber l3 in which the raw mate rial is worked. Communication between conduit l2 and chamber l3'is prevented at times, by a slidably mounted gate I4. K h,

in the chamber l3, as best showjn Fig. 2,

t longitudinal vertical section of a I machine embodying the invention;

there is a pair of rolls I5 and I6 rotatably mounted on shaft l'l--ll. Chamber i3 is connected by a conduit iii to a hopper [9 in which the powdered materials are placed. The material is forced down into the conduit l8 and the chamber 83 by a ram 20 operated by suitable means such as an air cylinder 2|. The rolls l5 and I6 and the chamber 13 are preferably shaped like the corresponding 'parts-ofBanbury mixers or equivalent' mechanism. The shafts l'll'l carrying the'rotors' Iii-and l6-are driven by a motor 22, (Fig. 1). During operation-of the rotors, communication between the chamber l3 and the conduit' i2 is prevented when the gate or closure [4 ismo'ved to the position shown in Fig. 5. Dur- 'ing'-operation of the'r'otors the conduit I8 will falso'be closed off-by thehead 23 of the ram 20'.

Thus during the Working of the material the chamber Isis closed and the rolls [5 and I6 therein give the confined material a twisting and turning motion'which is sufiicient to engender enough heat in the'interior of the mass to plasticizeit thoroughly.

When the material is prepared and ready for molding, the gate I 4 is withdrawn to the posi- -tion shown in Figs. 1 and 4. This is done by a "reciprocable air cylinder 24 with a'fixed piston 25. The gate is secured to the cylinder 24 and is moved with it. Secured to the cylinder 24 at opposite sides thereof there are cam bars 26-2'6 (Figs. 1, 4 and 5) which are provided with a series of inclined cam portions 26a. Cam bars 2? 21s1idably mounted beneath the cam bars 26 are' likewise providd with inclined cam portions Tidwhichengag the inclined cam portions 26a of thecarn bar 28. The design and arrangen'ient of the cam bars 26-46 and 21-21 is such that when the cylinder 24 is advanced to move the gate I4 from its open position (Figs. 1 and 4) to its closedposition '(Fig. 5) the cam bars 21-21 will be carried along with the cylinder until they engage abutments 281 just before the cylinder reaches the limitof its stroke. Thereafter, as the cylinder continuesits inward motion, the gate is'moved upwardly to Wedge it against its seat; in the walls surrounding the chamber l3. When the gate is retracted the order of these steps is reversed so that the gate is first unseated and then withdrawn during which operation the cam bars 21 are returned to the position shown in ,Fig. 3.. The opening and closing of the gate are"controlled byelectrical control mechanism hereinafter described; When the gate is open, the prepared material is discharged through the conduitfl At this time, the segments ID and I I are separated as shown in Fig. 3 to open port 9. The cylinder segments if! and II are reciprocally moved by rams 30 and 3! which are operated by pistons 32 and 33 in hydraulic cylinders 34 and 35. 1

The mold sections, which are not shown in the drawings, are placed between the platens 7 and 8. The forward platen 1 may be=moved away from the nozzle for the purpose of changing the form of nozzle or for the purpose of cleaning, but during use of the machine will be held fixed in position against the forward end of the ma chine and held braced .by rods 40 and 4|. The platen 3 is moved by a ram 42 urged by a piston 43 in a hydraulic cylinder 44 receiving fluid pressure from hydraulic lines 45- 15.

Hydraulic pressure for each hydraulic cylinder above mentioned is derived from a pumping unit 46 which may in practice comprise a series of as many as four to six pumps driven by a power unit 4! which may in practice comprise a series of :motors. A tank 48 supplies the oil for the system and serves as a reservoir during idle circulation of the oil; The conduits 49 supply fluid and pressure to the hydraulic cylinders, and conduits 56 provide --for return flow. The hydraulic and air cylinders are controlled by the electrically operated valves hereinafter described.

In order to understand the nature and operation of the controlmechanism, Figs. 1 and '7 may be considered jointly.

In Fig. 7, 60 indicatesdiagrammatically asafety gate or fence which is used to insure that the worker cannot put his handsin-the machine during operation and so Joe injured. Thisfence 60 when closed activates a star-terswitch 6| which initiates the train of operation hereinafter described. Both-the fence and-the starter switch aremerely indicated schematically.

Atthe beginning-of the cycle, safety fence B is manuallyclosed and pushes the starter switch 6|. This energizes a control 62 which in turn activates a valve -63 causing the a'ircylinder 2| to operate the ramZil (Fig. 1) which feeds material from'the hopper l9 to the chamber I3.

Gontrol- 62 is a form of timer switch common in the art. This control =6-Z;r-uns through its'cycle and at the end of its cycle-closes the valve 63 which shuts off the air to cylinder -2 -l so that feed to the chamber -l3-by;movement of the feed ram is stopped. =At the lower end of its stroke this ram compacts the =material in the chamber I3, and in its lowermost positionwhen-stationary serves as the top of the chamber !3. At this time control 62 energizes control switch 64' which in turn governs the working time of the material in the chamber l3. 1 The working continues until the desired state of plasticity is obtained in the material, without scorching or setting. This may be regulated by thermostatic control or by 'time control, either providing that the material will be worked until thoroughly --plasticized. Control B t-then at the end of its predetermined-heat or time ;cycle energizes control 65 which actuates valve 66 which causes the .plasticized material'to be dumped by operating the air cylinder 24which causesthe gate or door M at the bottom of the chamber I3 to be drawn to one side to permit communication with the conduit l2. At this-stage of the operation the segments In -and H are standing withdrawn in theiropen position (Fig. 3) and the plasticized materialis discharged and drops freely into the injection cylinder 2 ahead of the injection'ram which is nowstandingjwith When the material has been placed in the cylinder the control 65 actuates valve 6'! which causes the injection cylinder segments to close by the operation of paired hydraulic cylinders 34 and 35 and rams 30 and 3i (Fig. 2). When the segments are completely closed (Fig. 2) a segment interlock switch 68 actuates either control- 69 or control ll] according tothe setting of a manually controlled switch ll. Depending on whether control switch 10 or control switch 69 is activated, the machine will proceed to injectinto the mold the charge of material in the injection cylinder, or will compact the material therein and supply another charge and then in- .ject it into the mold.

Assuming that control switch 10 is energized, 'th'en 'control'i'fl energizes control 8!! which operates valve M which causes the mold cylinder 44 to move mold clampingfram 4'2 forward to close the mold. -At the same time, control 65 energizes either control "82 or control '83; depending on the setting of switch '1 I. If switch H is turned to activate switchi'll, then control 83'i's activated. oritrol 83 energizes dbhtibT'SViitCiiM 'to' initiate a cycle thereof. -In timedrelation contrbl switch it operates Valv85 which causes hydraulic 'cylinder '4 to move the ram "l to 'in'j ec'tthe' material into the mold. The-'machine'stays in -this position a redetermined Ien'gthof time as determined by control valv'e Hi. When the'time has elapsed, control I0 functions to operate valve 85 again and, with the changed setting of the valve, the hydraulic cylinder 4 causes retraction of the ram l. Simultaneously, "the segments 11] and II are "retracted to 'op'e'nlport "9, as valve 61 is operated with valve 85 =on the return stroke of the injection rain "I 'ithe complete cycle of control ill activating control 65. Withth'e ram all the way backthifiaclihi refriaihsin this position until the setting of control 85 is reached, "whereupon it operates'va'lve' 8 i againand "themold clamping ram is"ret r'act'ed"to'open themo'ld. When the mold is fullyT113811;"all(zl itftils'except control a l are automatically reset for a new cycle. With "the inolcr'operithe operator can open the safety fenc'e; By this time oontrolBi has run its cycle" and, if theautomatic repeat cycle control 86 is on, the machine will go through its operative plasticfzin'g and molding 1 cycle *when the safetyfence Bl) is again closed by the operator thus 'clos'ing thesta'i-tihg switch 6|. The pumping unit 46 supplies oil under pressure to move the severalflr'pis'tons' "of the hydraulic cylinders, the oil-being automatically by passed by relief 'v'alves control save-earmado not call for operation of the'ramsj "If the platen I is moved by a hydraulic cylinder, itsoperation Will 'be annually-cont nued, and so is not related to the c'ycle of operations-abovedescribed.

In the secon'drhe'thod o'f operation, the m'anual switch "H is set to cause the*in-ie'c'ti'on cylinder to receive two charges of "the ma'terial b'forein jec'tion takespl'ac'e e first charge of-"mat'e'rial being compatedbf re admission ofthesecond charge. In 'this 'even't,assumingthat preliminary feeding, working and dumpinghaveaneady taken place, -asdescribed"abdve,"-'eontrol- 68 energizes control 69 instead-of control 11). -Control switch 69 energizes "valves '85 a'nd ilfl', which *cause' 'the inje'ctionram I to mrWa-rdumert w pressure by operation "ofcyli'nder *4. ftValv'e' 9| regulates the low Lpre'ssurefiby-paSsingthe excess oilto the tank. v

The forward .moverrieritfofithuam "compacts :energizsgcontrul-flZ which in turn; energizes valve 63. .This {causes asnew- .charge:,of,material to. be placed in chamber l3 by action of the air cylinder 2Iaand' 'raHiZQBKiWliemcontrobfl ends its cycle material is no longer fed to the mixing chamber and again the'he ad ZB "of the s'tationary ram 235 1 11 t -b he ch mber Atihis gramme-1 b back by operation of hydraulic 'cylinder- 4 which-- is controlledby valve 85 and simul- --ta'neoii'sly the segments ar'e opeiied by the action of hydraulic cylinders 34 and 35 controlled by valve 61. Also when control 82 energizes control 92 it likewise energizes control 80 which in turn causes the mold clamping ram 42 to go forward due to action of hydraulic cylinder 44 which is controlled by valve 8|. When control 92 functions it also causes operation of valve 66 and the material is dumped from the chamber l3 to the injection cylinder 2 through the port 9.

When the injection cylinder is fully charged control 83 operates to energize control '84 and also energizes valve which causes the segments to be closed, by action of the hydraulic cylinders 34 and 35.

When the segments I 0 and II are closed segment interlock I60 energizes control which in turn energizes valve 85 alone causing the injection ram l to go forward under high pressure under the action of the hydraulic cylinder 4 as I previously described in the first mode of operation. This action causes the combined charges of material to be forced into the mold.

The ram remains in its forward position a predetermined time as determined by control 69, whereupon as heretofore described valve 85 is again operated and, with the changed setting of the valve, the ram l is retracted and the injection cycle is completed, allowing control 65 to operate valve 61 and cause the segments ID and II to be retracted as the ram returns. Then, as heretofore, the setting of control 85 is reached and valve 8| is operated to open the mold, and all controls except 84 are automatically reset for a new cycle. When control 84 completes its cycle, the complete sequence of operations of the machine will be repeated if automatic control 86 is on.

In a third method of operation the ram is caused to inject only a part of the material supplied to the injection cylinder at one molding so that a plurality of moldings are made for each charge. This is done by operating the relief valve .in the injection cylinder line to reduce the pressure behind the ram to a point where it is held stationary at the end of the first short stroke, then increasing the pressure after the molds have been emptied and closed so as to inject a second charge, and repeating until the ram has been advanced the full distance to the end of its travel and all of the charge has been utilized in successive moldings. Since the ram is not withdrawn between successive short strokes, the segments will not open until the last injection is completed and the ram returns to its starting position.

The machine may be used for either thermo- ,struction of these valves does not constitute a radii-8.54

material,the nozzle 6 is removed and the nozzle @iia shown in, Fig. 6 is inserted in its place, either nozzle fitting into the bore 61) at the end of the injection cylinder. Y

Theelectricalswitches usedare known types of. time andllmitswitches, andthe, valves used are common in the field of hydraulic engineering. major. valves. arefour- -way valves having spools acted upon by supplemental; hydraulic lines and, if desired, activated by pilotvalvesemploying solenoids, The word valve is sometimes used to indicate a valve unit or system. The conpartof the invention. I l The machine of the invention provides a greater degree of variability in operation than known 20.

molding, machines, and is particularly adaptedgto mold a great many small articles in a short time if the third method is used or a single very large article if the first or second methods are used. The material is taken from the working chamber at the moment when it is ready to mold and is maintained in this condition if not immediately molded by heating the injection cylinder enough to maintain the temperature of the material but not enough to increase it. The molding follows automatically and in timed relation to the working. Also, it is possible to use a relatively short stroke, as it is not necessary for the ram to condense a large bulk of unprepared material or to serve as means for shutting the feed port.

I claim:

1. In a machine for molding plastic material, in combination, an injection cylinder, an injection ram in said cylinder, means for moving the ram, a pre-plasticizing chamber spaced from the cylinder, a conduit connecting the chamber and the cylinder, said conduit including a port in said chamber and a port in said cylinder, a closure means for the first named port adapted to form a part of the chamber wall and a second closure means for the second named port adapted to form a part of the cylinder wall.

2. A machine for molding plastic materials having, in combination, an injection cylinder, an injection ram in the cylinder, a chamber for holding plasticizable material spaced from the cylinder, rotors within said chamber adapted to give said material a twisting and churning motion creating heat therein by internal friction, means for giving said rotors a continuous rotative motion during operation of said machine, a port in the bottom of the chamber, a closure for the port, means for moving the closure, a port in the top of the injection cylinder, a closure for said port, hydraulic means for moving said injection ram and said second named closure, a control mechanism which regulates the action of said firstnamed closure moving means and a second control mechanism responsive to said first control mechanism which initiates operation of said hydraulic means first to close said second port and in timed sequence thereto move the injection ram through a cycle of molding operations.

3. In a machine for molding plastic material, in combination, an injection cylinder, an injection ram in said cylinder, means for moving the ram, a pre-plasticizing chamber spaced from the cylinder, a conduit connecting the chamber and the cylinder, said conduit including a port in said chamber and a port in said cylinder, a closure naem rbi the first named port aaaptea m rom 'a pa rt of thebhxmber wau and a second lo'sure :means idrthe second named port adapted Mid-fin a a'irt df the cylinder wallg 'oi'itr bl-fme'alfis fqr "'1" tile/fling 'ithe p'lasticizing of matrial in the dhambrparid' control means responsivethereto for operating said second closure-means. m a-maohinefor moldingplastic'materi-oil, in

means or the'first named port adapted #:o '1

means forthe second named *porp-a'daptdfio farm; a; part of; the =cy1inder W511; control nieens mimosa fnr' oiiethting sici second-elosure meaiisg'afidediirm xficlidnism Gpemtedmy-said: seoondxiclosure *main's ibr iiiitialting movement 0mm ram.

PREFERENCES CITED i "The: foiiowirig' references are --of 'record mime 

